Continuous processing system

ABSTRACT

A manufacturing system utilizing a plurality of satellite functional processing stations or sectors, each capable of standalone operation. The stations are interconnected by a handler or conveyor, which will transport individual ones of work-pieces from one processing station to the next in accordance with a prescribed sequence corresponding to the processing requirements for the workpiece.

United States Patent Aronsatein et al.

CONTINUOUS PROCESSING SYSTEM Inventors: Jesse Aronstein; William E.

Harding, both of Poughkeepsie, N.Y.

International Business Machines Corporation, Armonk, NY.

Filed: Feb. 5, I973 App]. No.: 329,920

Assignee:

US. Cl. 29/569; 29/563; ll8/6 Int. Cl B01] 17/00 Field of Search 29/569, 33 P, 563; llS/6 References Cited UNITED STATES PATENTS 12/1970 Perry 29/563 INPUT 1 June 17, 1975 3,576,540 4/:971 Fair ..29/563 3,618,!99 ll/l97l King ..29/569 Primary ExaminerW. Tupman Attorney, Agent, or Firm-Henry Powers [57] ABSTRACT 10 Claims, 25 Drawing Figures PATENTEIJJUN 17 I975 SHEET PATENTEIJJUN 1 7 I975 SHEET l null PATENTEDJUN 17 1915 SHEET FIG. 9

HANDLER CONTROL SYSTEM FIG. 10 SENSOR BASED BASIC CONTROL svsren PATENTEDJUN I T 1975 SHEET I O 200 START CHECK TRANSSORT BUSY BUSY 202 CHECK EACH PROCESS SECTOR IF ALL FOLLOWING CONDITIONS ARE MET:

ALL CONDITION NOT MET s 0 IF OUTPUT PEDESTAL FOR SEcTOR (k) IS OCCUPIED IF NEXT SECTOR (k +1) IN SEQUENCE IS OPERATIVE QT ECEEE E I I PI SE NE EEEPQQS QUENCE IS AVAILABLE IN SEQUENCE SEKTOR (K) EXIST 209 WHERE ALL CONDITIONS MET SEND TRANSPORT /2 3 T0 PICK UP WORK- PIEcE AT SECTOR DlRECT TRANSPORT SYSTEM (k) AND uNLOAD T0 PICK UP WORK-PIECE AT FROM SYSTEM OuTPuT PEDESTAL OF SECTOR (k) AND DELIvER TO INPuT PEDESTAL 0F SECTOR (k +1) mm TRANSP RT BUSY SIGNAL ON M204 UNTIL TRANSFER TURN TRANSPORT SYSTEM MADE BUSY SIGNAL ON UNTIL wORI -PIEcE TRANSFER Is MADE WORK-PIECE LAST TO BE PROCESSED FIG. 15

PATENTEIIJUII I 7 ms 3.889355 SHEEI I I FIG. FIG. @205 I;- 168 16A HG FIG.I6A P FIG. I6 CHECK BUSY TRANSPORT BUSY SIGNAL NOT CHECK IF WORK-PIECE OCCUPIES AN OUTPUT STATION OF A SELECTED SECTOR (I) UTILIZED TWICE IN A SEQUENCE OF SECTORS IS SECTOR (III LAST SECTOR IN SEQUENCE CHECK IF INPUT POSITION AVAILABLE IN NEXT SECTOR (2+ 1) WHOSE 215 NOT ADDRESS IS SPECIFIED IN SEND TRANSPORT TO AVAILABLE REGISTER OF SECTOR (X) TO PICK SECTOR g UP WORK-PIECE AND UNLOAD FROM SYSTEM i AVAILABLE I -2I6 220 TURN TRANSPORT BUSY SIGNAL ON UNTIL TRANSFER MADE DIRECT TRANSPORT TO PICK UP WORK-PIECE AT OUTPUT POSITION OF SELECTED SELECTOR (HAND TRANSFER TO INPUT POSITION OF NEXT SECTOR I +DWHOSE ADDRESS IS SPECIFIED IN REGISTER OF SELECTED SECTOR II) IS WORK-PIECE LAST TO BE PROCESSED TURN TRANSPORT BUSY INDICATOR ON UNTIL TRANSFER IS MADE PATENTEOJUN I 7 I975 3 8 A SHEET 12 US'OSS CHECK IF LOADING POSITIONS OF SELECTED SECTOR I!) OCCUPIED BY A WORK-PIECE OOOUPIEO CHECK SUCCESSIVELY FOR A FIRST SECTOR (k) IN REMAINDER OF SECTORS SEQUENCE EXCLUDING (D FOR FOLLOWING CONDITIONS:

. UNLOAD POSITION OCCUPIED BY A WORK-PIECE SECTOR (X) IS NEXT SECTOR IN SEQUENCE LOAD POSITION OF NEXT SECTOR (k 1) OF REMAINDER OF SECTORS EXCLUDING (1) IS AVAILABLE ALL 0 SECTOR (k 1)TO FOLLOW CONDITIONS SECTOR (1) IN SEQUENCE NOT NET 0 NO WORK-PIECE IN SECTOR (R) DESTINED FOR SECTOR (k 1) ALL CONDITIONS MET r224 SEND TRANSPORT TO SECTOR (k) & PICK UP WORK-PIECE AND TRANSFER TO SECTOR I!) PLACE ADDRESS OF NEXT SECTOR (k 1) TO FOLLOW SECTOR (1) IN REGISTER OF SECTOR (1) TURN TRANSPORT BUSY INDICATOR ON UNTIL TRANSFER IS MADE FIG. 16B

PATENTEUJUN I T ms 3. 889,355

SHEET 13 CHECK sUcCESSIvELY FOR 225 A FIRST SECTOR (k) IN REMAINDER 0F sECToRS IN SEQUENCE FOR FOLLOWING CONDITIONS:

. HAS UNLOADING PosITIoN ALL OCCUPIED BY A WORK- CONDITIONS PIECE NOT MET IF A NEXT SECTOR (k 1) IS TO IMMEDIATELY FOLLOW SECTOR (k) IN RENIAINDER 0F (S2E)CT0R SEQUENCE EXCLUDING 0 IF SECToR (k 1) IS OPERATIVE 0 IF SECTOR (k 1) HAS LOADING PosITI0N AVAILABLE ALL CONDITIONS MET SECTOR (k) LAST SECToR IN SEQUENCE SEEIIRII'II ASIJI u WORK-PIECE AND TRANSFER EF EE 'SSEEF S AND To SECTOR 1) UNLOAD FROM SYSTEM I 1 TURN TRANSPQRT BUSY TURN TRANSPORT BUSY INDICATORON UNTIL TRANSFER |ND|CAT0R ONUNTIL TRANSFER MADE MADE WORK-PIECE LAST TO BE PROCESSED FIG. 16C 7 SHEET I4 FIG. FIG. START 17B 17A A HG FIG. 17A P we FIG. 1? CHECK TRANSPORT BUSY SIGNAL CHECK OUTPUT POSITION OF EACH DUPLICATED SECTORS (I) UNTIL FIRST WORK-PIECE PRESENT SIGNAL FOUND OR UNTIL ALL DUPLICATED SECTORS CHECKED NOT OCCUPIED OCCUPIED IS SECTOR (I) LAST SECTOR IN SEQUENCE 246 CHECK IF INPUT POSITION AVAILABLE IN NEXT SECTOR I I l) WHOSE ADDRESS IS SPECIFIED IN REGISTER OF SECTOR III f 245 SEND TRANSPORT TO SECTORIIITO PICK UP WORK-PIECE AND UNLOAD FROM SYSTEM 250 AVAILABLE TURN TRANSPORT BUSY DIRECT TRANSPORT SIGNAL ON UNTIL TO PICK UP WORK- TRANSFER MADE PIECE AT OUTPUT OF SECTOR (1)8 DROP IT OFF AT INPUT OF SECTOR (1+ 1) WHOSE ADDRESS IS SPECIFIED BY CON- TENTS OF THE SECT- OR (I) DESTINATION REGISTER IS WORK-PIECE LAST TO BE PROCESSED PATENTEDJUII 1 T ms 3,889.3 55 SHEET 1 CHECK IF LOADING POSITION OF DUPLICATED SECTOR (1) OCCUPIED BY A WORK-PIECE OCCUPIED CHECK 252 SUCCESSIVELY FOR A FIRST SECTOR (k) m REMAINDER OF SECTOR SEQUENCE,EXCLUDING SECTORII) FOR ALL FOLLOWING CONDITIONS:

Q UNLOAD POSITION OCCUPIED BY A WORK- PIECE SECTORIUNEXT SECTOR IN SEQUENCE LOAD POSITION AVAILABLE IN NEXT SECTOR (k 1) OF REMAINDER OF SECTORS,EXCLUDING SECTOR (1) 0 SECTOR (k 1) TO FOLLOW SECTORIR) IN SEQUENCE 0 NO WORK-PIECE IN SECTOR ")DESTINED FOR SECTOR (k 1) ALL CONDITIONS NOT MET BY ANY SECTOR ALL CONDITIONS NET BY SECTOR I SEND TRANSPORT T0 SECTOR (k) T0 PICK UP WORK-PIECE AND TRANS- FER To SECTOR I) PLACE ADDRESS OF NEXT SECTOR (k 1) TO FOLLOW SECTOR) IN REGISTER OF SECTOR) TURN TRANSFER BUSY SIGNAL ON UNTIL TRANSFER MADE FIG. 17B

PATENTEIJJIIII I 7 I975 16 CHECK SUCCESSIVELY FOR A FIRST SECTOR (k) IN REMAINDER OF SECTORS IN SEQUENCE FOR FOLLOWING CONDITIONS:

0 HAS UNLOADING POSITION EXCLUDING SECTOR I I I POSITION AVAILABLE OCCUPIED BY A WORK-PIECE 0 IF NEXT SECTOR (k 1) IS TO IMMEDIATELY FOLLOW SECTOR (k) IN REMAINDER OF SECTORS Q IF SECTOR (k+l) IS OPERATIVE IF SECTOR (k l) HAS LOADING ALL CONDITIONS NOT MET ALL OONOITIONS MET IS SECTOR (k) LAST SECTOR IN SEQUENCE SEND TRANSPORT TO I SECTOR (k) TO PICK UP SEND TRANSPORT T0 WORK-PIECE AND TRANS- SECTOR (k) TO PICK FER TO SECTOR (k 1) UP WORK-PIECE AND UNLOAD FROM SYSTEM TURN TRANSPORT BUSY TURN TRANSPORT BUSY SIGNAL ON UNTIL TRANSFER SIGNAL ON UNTIL TRANS- MADE A FER MADE FIG. 17C

IS WORK-PIECE LAST TO BE PROCESSED PATENTEDJUII 1 7 I975 SHEET FIG. 18A

I START AVAILABLE NONE N0 WAFER PRESENT CHECK INPUT PEDESTAL OF EACH PATTERN GENERATOR SECTORS UNTIL EITHER 1. AN AVAILABLE PATTERN GENERATOR INPUT IS FOUND AVAILABLE INPUT 2. ALL ARE CHECKED AND NONE CHECK TRANSPORT BUSY SIGNAL CHECK OUTPUT PEDESTAL OF EACH PATTERN GENERATOR UNTIL FIRST"WAFER PRESENT" SIGNAL IS FOUND OR UNTIL ALL PATTERN GENERATORS HAVE BEEN CHECKED BUSY WAFER PRESENT AVAILABLE AT PATTERN GENERATIIRUI) SEND TRANSPORT TO PICKUP WAFER AT OUTPUT PEDESTAL OF PATTERN GENERATOR (1) AND DROP IT OFF AT INPUT PEDESTAL OF THE SECTOR WHOSE ADDRESS IS SPECIFIED BY THECONTENTS OF THE "PATTERN GENERATOR DESTI- NATION REGISTER" FOR PAT- TERN GENERATOR TURN TRANSPORT BUSY INDICATOR ON AND KEEP ON UNTIL MOVE IS COMPLETED L/ZTO PATENTEDJUN I 7 I975 N0 SECTOR EXISTS WHERE ALL BONDITIOIIS ARE NET HAS LAST WAFER BEEN PROCESSED SIIEET I 8 CHECK EACH PROCESS SECTOR (k) TO DETERMINE IF ALL THE FOLLOW- ING CONDITIONS ARE MET:

' OUTPUT PEDESTAL FOR PROCESS SECTOR (k) OCCUPIED BY A WAFER INPUT PEDESTAL FOR PROCESS SECTOR (k 1) IS AVAILABLE TO RECEIVE A WAFER PROCESS SECTOR (k 1) IS OPERATIVE THERE IS NO WAFER IN ANY PATTERN GENERATOR SECTOR DESTINED FOR PROCESS SECTOR (k 1) A SECTOR (k) EXISTS ARE MET WHERE ALL CONDITIONS DIRECT-TRANSPORT TO PICK UP WAFER AT OUTPUT PEDESTAL OF PROCESS SECTOR (k) AND DELIVER TO INPUT OF PATTERN GENERATOR PLACE ADDRESS OF NEXT PROCESS SECTOR (k 1) TO BE VISITED (AFTER THE PATTERN GENERATOR) INTO "DESTINATION REGISTER" FOR PATTERN GENERATOR R TURN TRANSPORT BUSY INDICATOR ON AND KEEP ON UNTIL MOVE IS COMPLETED FIG. 18B

CONTINUOUS PROCESSING SYSTEM FIELD OF THE INVENTION This invention is directed to a complete manufacturing system which has capability of fast turn-around, maximized yield and low in-process inventory. More specifically, the manufacturing system of this invention is directed to operations involving the processing of multiple part numbers wherein the cost of base material and processing is trivial with respect to the add-on value, and wherein the improvement comprises the interdependent minimization of processing cycle time and maximization of completed part yield.

Although the invention has general application to a wide range of manufacturing systems for processing a corresponding scope of work-pieces, it will be illustratively described with specific reference to a semiconductor manufacturing system to which environment the invention was developed.

DESCRIPTION OF PRIOR ART As background for the development of the invention in the semiconductor processing environment, it may be noted, that during the early 1960s the industry at large engaged in extensive manufacture of planar semiconductor structures, particularly with respect to silicon diodes and/or transistors. In the processing of semiconductor wafers (e.g. silicon), there were two clearly identifiable modes of batch processing. The first was the wafer itself, where, within it, batching was accomplished by forming a plurality of identical transistors or diodes. Typically, a l.25 inch diameter wafer could contain I000 transistors. For purposes of discussion, this mode of batch processing is defined as WAFER BATCHING."

A second mode of batching, herein called MULTI- PLE WAFER BATCHING" was also identifiable in various production lines. A typical example of the form of batching in a diffusion step, might employ the pro cessing of 200 wafers simultaneously.

In order to increase output and to lower costs, vari ous manufacturing systems developed throughout the 1960s exploited each of these batching modes.

With respect to WAFER BATCHING" it may be noted that this mode of operation does reduce the separate cost/device of each manufacturing step.

One way to improve the advantages of WAFER BATCHING" is by increasing the size of the wafer, which over the years has progressively increased in sequential steps from an initial diameter of 0.75 inches to presently advanced use of 3.25 inch diameter wafers. However, although such WAFER BATCI-IING" can economically improve thruput ofa system, it frequently requires significant re-tooling to accommodate its increasing wafer size. Jigs, handlers, racks, etc. may all have to be redesigned and old tools obsoleted. Frequently, significant process modifications must be developed (with their associated costs) to accommodate tool and process. For example, a completely new diffusion furnace design may be required for an increase in wafer size. In addition, extensions of WAFER BATCHING rarely raised yield, and in fact, tend to decrease it.

Examples of improvements over the years utilizing MULTIPLE WAFER BATCHING" are numerous, typical of which is the use from 8 to 18 and then up to 35 wafers in metallization operation; from 8 to 20 and then to wafers in epitaxial reactors, and from 10 wafers to as many as 300 batched wafers in diffusion operations.

This mode of batching has some significant negative consequences. First, it is usually done independently for each operation. Thus, the improvement enhances only the thruput and cost for that particular operation. Secondly, it leads to gross batch size mismatch throughout the line creating larger in-process inventories and, thirdly, the technique usually results in process times for the operation itself to be increased. Slight reduction in process yield for the operation is a common result. It should be pointed out that neither of these batching modes affects the number of chips which must be tested and this part of the fabrication contributes significantly to total chip cost.

With the advent of monolithic integrated circuits, a third batching mode was added which herein is called CHIP BATCI-IING." This third mode is simply the exploitation of large scale integration as seen and discussed within the semiconductor industries. Typically, this technologyqaermits the increase in the output of a single chip from one transistor to over I400 individual transistors and resistors in typical integrated circuits. Normally, this increase of more than I400 times is paid for by only increasing chip size.

It is the considered opinion of the inventors, of this application, that future improvements in the manufacturing system can make little or no gains in MULTI- PLE WAFER BATCHING." Similarly, systems based upon extensions of WAFER BATCHING can make few gains while running the risk in geometrical problems involving size fragility of wafers, mechanical registration, thermal gradients, etc. are likely to further degrade yields.

On the other hand, CHIP BATCHING" for large scale integration is just beginning with the potential of increasing thruput at least another factor of at least 10 at perhaps no more than at a price of increasing chip areas by factors of 2 to 4 times. Simultaneously, also obtained will be the added value of the integrated product, reduced testing cost minimized potential tooling changes and reduced packaging costs.

Irrespective of the batching mode employed, the fabrication of semiconductor devices involves a sequence of many process steps. The number of processing steps varies and is determined by the kind of product and its complexity. The sum of the times required to do all the steps and sequence is called PROCESSING TIME and is typically 40 to 60 hours of the total production time. Factories based upon MULTIPLE WAFER BATCHING" have longer PROCESSING TIME" because the tools, while handling many parts simultaneously, also have characteristics which add to the processing time (longer outgassing time or cooling time in an evaporator, for example). In addition their loading, unloading, and set up times are frequently longer.

In addition to the PROCESSING TIME," the total cycle time for wafer fabrication includes QUEUE times, which in fact make up the major part of the total time of fabrication. In todays manufacturing lines, total QUEUE times are typically 40 to 60 days. Wafers Queue for many reasons such as the time to assemble the MULTIPLE WAFER BATCH, equipment down time, waiting while masks are matched to job lot, etc. Individual times can become so long, that extra clean- 

1. A manufacturing system for processing semiconductor substrates comprising: A. a plurality of processing stations having loading and unloading positions, each of said stations having means for performing a plurality of different fixed semiconductor device fabricating operations on a said substrate, wherein a. one of said operations in at least one of said stations includes means for application of a coating of photo-resist on a surface of individual ones of said substrates; B. a conveyor means for detachably supporting and transporting individual ones of said substrates between and at any one of said work stations; C. means for detaching individual ones of said substrates from said conveyor means and transferring said individual ones of said substrates between said conveyor and said stations at their said loading and unloading positions; and D. control means for said conveyor and transfer means for routing said substrates individually between any prescribed sequence of said stations for a corresponding prescribed series of processing operations.
 2. The manufacturing system of claim 1 wherein said control means routes said individual ones of said substrates at least twice to and from a selected one of said stations.
 3. The manufacturing system of claim 1 wherein at least one of said stations is replicated at least twice to have substantially similar processing operations to which said substrates can be transferred from and to the remainder of said stations in accordance with said prescribed sequence.
 4. A manufacturing system for processing semiconductor substrates comprising: A. a conveyor means for transporting said substrates individually between and at any selected one of a plurality of locations along the path thereof; B. a plurality of processing stations at respective ones of said locations for performing semiconductor processing operations on said substrates and having loading and unloading stations for corresponding feeding and discharging of individual ones of said substrates, with at least three required sequential ones of said station having the first and third station disposed adjacent one end of said conveyor path and the second station of said sequence disposed adjacent the other end of said conveyor path, wherein a. one of said operations in at least one of said stations include means for applying a coating of photoresist on a surface of individual ones of said substrates; C. means for transferring said individual ones of said substrates between said conveyor and said stations at their said loading and unloading stations; D. control means for said conveyor and transfer means for routing said substrates individually between and at selected ones of a prescribed sequence of said stations for a corresponding sequence of processing operations therein.
 5. The manufacturing system of claim 4 including means for loading and unloading fresh and finished semiconductor substrates, respectively, into and from said prescribed sequence of stations.
 6. The manufacturing system of claim 4 wherein said control means includes means for routing said substrates at least twice to a selected one of said stations.
 7. The manufacturing system of claim 4 including means for loading and unloading new and finished semiconductor substrates, respectively, at prescribed first and last stations.
 8. The manufacturing system of claim 5 wherein at least one of said stations is replicated at least twice to have substantially similar processing operations to which said substrates can be transferred from and to the remainder of said stations in accordance with said prescribed sequence.
 9. A manufacturing system for processing semiconductor substrates comprising: A. a plurality of independent processing stations having means for performing at least one fixed semiconductor processing operation on said substrates and having loading and unloading positions, wherein a. one of said operations in at least one of said stations includes means for applying a coating of photoresist on a surface of individual ones of said substrates; B. means for transferring individual ones of said substrates between and at preselected ones of said stations from and to, respectively, the unloading and loading positions thereof, and C. control means for said transfer means for routing said individual ones of said substrates sequentially between and at any preselected one of said stations of a sequence of selected ones of said stations, and including means for specifying said prescribed sequence.
 10. The manufacturing system of claim 9 including means for loading and unloading fresh and finished semiconductor substrates, respectively, into and from said prescribed sequence of stations. 